CN111601863A - Surface protective film and optical member with protective film - Google Patents

Abstract

The surface protection film (10) is provided with a pressure-sensitive adhesive layer (2) which is fixedly laminated on the main surface of a film base material (1). The surface protection film has a haze of 2% or less. The surface-protecting film has an adhesion to an acrylic plate at a stretching speed of 30 m/min and a peel angle of 180 DEG of 0.03N/25mm or more. The total damage amount calculated from an image of 200 × 200 pixels obtained from an inspection area of 5mm × 5mm of the surface protective film is 3000 or less. The thickness of the pressure-sensitive adhesive layer (2) is preferably 2 μm or more. The film substrate (1) preferably contains substantially no particles.

Description

Surface protective film and optical member with protective film

technical field

The present invention relates to a surface protection film including an adhesive layer on a film base material, and an optical member to which the surface protection film is bonded.

Background technique

Surface protection films are provided on the surfaces of optical devices such as displays and imaging devices, electronic devices, thin films, glass materials, and the like as constituent members of these devices for the purpose of surface protection, imparting impact resistance, and the like. The surface protective film includes a surface protective film (surface protective film used as a process material) that is temporarily adhered in a state before use, such as assembly, processing, and transportation of the device, and peeled again before use of the device (surface protective film used as a process material), A surface protective film (surface protective film for the purpose of permanent adhesion) that is used in a state of being attached to the surface of the device when the device is used.

Both the surface protection film used as a process material and the surface protection film for the purpose of permanent bonding are provided with an adhesive layer on the main surface of the film substrate, and are bonded to the adherend to be protected through the adhesive layer. surface (for example, refer to Patent Document 1).

As a base material of a surface protective film, polyester film is widely used because it is excellent in mechanical strength and transparency. In a polyester film, generally, fine protrusions are formed on the surface by compounding particles in a resin to improve sliding properties, winding characteristics, and the like (for example, refer to Patent Document 2).

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2013-79360

Patent Document 2: Japanese Patent Laid-Open No. 2006-176685

SUMMARY OF THE INVENTION

Invention to solve problem

If the transmitted light from the adherend is visually recognized in the state where the conventional surface protection film using a polyester film is attached to the adherend, the deformation of the transmitted light occurs, or the glare of the transmitted light is visible, and the visibility decreases. Case. This tendency becomes remarkable especially when sticking a surface protection film on the surface of a display device, such as a display, and visually recognizing from a short distance. Image distortion and glare caused by such a surface protection film hinder optical inspection and imaging.

In view of the above, an object of the present invention is to provide a surface protection film that has good adhesion to an adherend and is less likely to hinder visual recognition and imaging of transmitted light from the adherend.

solution to the problem

The surface protection film of this invention is provided with the adhesive layer fixed and laminated on the main surface of a film base material. The haze of the surface protective film is 2% or less. The adhesive force of the surface protection film to the acrylic sheet is 0.03N/25mm or more. The adhesive strength is a measured value based on a peel test at a tensile speed of 30 m/min and a peel angle of 180°. The surface protection film preferably has a total damage amount calculated from an image of 200×200 pixels obtained from an inspection area of 5 mm×5 mm to be 3000 or less.

The thickness of the adhesive layer is preferably 2 μm or more. The pressure-sensitive adhesive layer preferably contains at least one selected from the group consisting of acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, and silicone pressure-sensitive adhesives.

The film substrate is preferably substantially free of particles.

effect of invention

Since the surface protective film of the present invention has good adhesion to the adherend, the incorporation of air bubbles into the bonding interface is unlikely to occur, and the surface protective film is excellent in visibility in a state where the surface protective film is bonded to the adherend. In addition, the surface protective film has a low haze and is unlikely to cause scattering of light, so it is unlikely to hinder the visual recognition and imaging of the transmitted light from the adherend, and has good visibility.

Description of drawings

FIG. 1 is a cross-sectional view showing a laminated structure of a surface protection film.

FIG. 2 is a cross-sectional view showing a laminated structure of a surface protection film to which a separator is temporarily adhered.

Detailed ways

[Constitution of Surface Protection Film]

FIG. 1 is a cross-sectional view showing an embodiment of a surface protection film. The surface protection film 10 includes the pressure-sensitive adhesive layer 2 on the first main surface of the film substrate 1 . The adhesive layer 2 is fixedly laminated on the first main surface of the film base 1 .

As shown in FIG. 2 , the separator 5 may be temporarily adhered to the pressure-sensitive adhesive layer 2 of the surface protection film 10 . The surface of the adherend can be protected by peeling off and removing the separator 5 temporarily adhered to the surface of the pressure-sensitive adhesive layer 2 and bonding the exposed surface of the pressure-sensitive adhesive layer 2 to the adherend. In addition, "fixing" means a state in which the two laminated layers are firmly adhered, and peeling at the interface between the two is impossible or difficult. The "temporary adhesion" refers to a state in which the adhesive force between the two laminated layers is small and can be easily peeled off at the interface between the two.

<Adhesion>

It is preferable that the adhesive force of the surface protection film with respect to an acrylic board is 0.03 N/25mm or more. When the adhesive force is 0.03 N/25 mm or more, the mixing of air bubbles between the pressure-sensitive adhesive layer 2 of the surface protective film and the adherend tends to be less likely to occur, and the image clarity tends to improve. The adhesive force of the surface protective film to the acrylic plate is more preferably 0.05 N/25 mm or more, and still more preferably 0.07 N/25 mm or more.

The upper limit of the adhesive force of the surface protective film to the acrylic plate is not particularly limited. When the surface protection film is used as a process material and the releasability from the adherend is required, the adhesive force to the acrylic sheet is preferably 10 N/25mm or less, more preferably 5N/25mm or less, and still more preferably 3N/25mm or less. When re-peelability is required, the adhesive force of the surface protection film to the acrylic plate is preferably 1 N/25 mm or less.

The adhesion force to the acrylic plate is the peel force when the surface protection film is attached to the acrylic plate and left to stand for 30 minutes in an environment of 23° C., and then subjected to a 180° peel test at a tensile speed of 30 m/min. The smaller the adhesive force is, the easier the high-speed peeling of the surface protective film from the adherend is, and the adhesive residue on the adherend and the breakage of the surface protective film during peeling are less likely to occur, and the workability is excellent. The adhesive force of the surface protection film 10 mainly depends on the characteristics of the adhesive layer 2 .

<Haze>

The haze of the surface protective film is preferably 2% or less, and more preferably 1.5% or less. By making the haze of the surface protective film small, the visibility when the adherend is visually recognized through the surface protective film is excellent.

<Total damage amount>

The total damage amount of the surface protective film is preferably 3,000 or less, more preferably 2,500 or less, and even more preferably 2,000 or less. The smaller the total damage amount, the smaller the unevenness of the brightness of the light transmitted through the surface protective film, and the tendency for glare to be suppressed. In addition, there is a tendency that the smaller the total damage amount is, the more the image sharpness is improved.

The total damage amount was obtained by irradiating light from the glass plate side with a surface light source while moving the sample obtained by bonding the surface protection film to the glass plate at a linear speed of 5 m/min, and using a line scan camera (KEYENCE CORPORATION "XG-HL04M" manufactured by KEYENCE CORPORATION) imaged the transmitted light, and analyzed the obtained image with a damage inspection tool manufactured by KEYENCE CORPORATION. The distance between the light source and the sample at the time of imaging was 200 mm, and the distance between the sample and the line scan camera was 210 mm. The segment size at the time of analysis was set to 4, and the damage level threshold was set to 3.

The total damage amount is: the area where the difference in brightness (damage level) of the image captured by the line scan camera (gray scale 256 levels) exceeds the threshold value is counted as "damage", and counted in the shooting area as The number of "damaged" segments. The damage level is the difference between the maximum value and the minimum value of the luminance in the four small regions in the moving direction of the set segment. When the difference between the maximum value and the minimum value of luminance in the four small areas exceeds the threshold value, the segment including the four small areas is counted as "damage".

<Image sharpness>

The clarity of the transmitted image of the surface protection film at a comb width of 0.125 mm is preferably 92.5% or more. The clarity of the transmitted image was measured in accordance with JIS K7374 (Plastics - Method for Determination of Image Clarity) using a sample obtained by bonding a surface protection film to a glass plate. The higher the clarity of the transmitted image, the less the glare of light transmitted through the surface protective film from the adherend, and the tendency for visibility to improve. When the clarity of the transmitted image is less than 92.5%, when the adherend to which the surface protection film is bonded is visually recognized from a short distance (eg, within 200 mm), glare is felt, and the visibility decreases. When the resolution of the transmitted image is small, it may adversely affect the imaging performed at a close distance from the object, such as fingerprint authentication. From the viewpoint of reducing the glare of transmitted light, the transmitted image clarity of the surface protective film is preferably 93% or more, more preferably 94% or more, and further preferably 95% or more. When the clarity of the transmitted image is 95% or more, the glare of the transmitted light is hardly felt even when the adherend is observed from a very close distance.

[Film substrate]

As the film substrate 1, a transparent plastic film can be used. The total light transmittance of the film substrate 1 is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. The haze of the film substrate 1 is preferably 1.5% or less, more preferably 1% or less, and further preferably 0.5% or less. The thickness of the film base material is, for example, about 5 to 500 μm. The thickness of the film substrate 1 is preferably 10 to 300 μm, more preferably 15 to 200 μm, and even more preferably 20 to 150 μm, from the viewpoint of both the protection performance and flexibility of the adherend.

As the resin material constituting the film base material, a resin material excellent in transparency, mechanical strength, and thermal stability is preferable. Specific examples of the resin material include cellulose-based resins such as cellulose triacetate, polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, polyamide-based resins, and polyimide Amine-based resins, polyolefin-based resins, acrylic-based resins, cyclic polyolefin-based resins (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof. In particular, polyester-based resins are preferable, and among them, polyester resins with a small amount of oligomers are preferable.

The film substrate may contain antioxidants, ultraviolet absorbers, light stabilizers, nucleating agents, fillers, pigments, surfactants, antistatic agents, and the like. An easy-adhesion layer, an easy-slip layer, an anti-blocking layer, an antistatic layer, an anti-reflection layer, an oligomer-preventing layer, etc. may be provided on the surface of the film substrate.

The film substrate is preferably substantially free of particles. By making the film base material free of particles, light scattering by the surface protective film is less likely to occur, and the in-plane uniformity of the surface shape is improved. Accordingly, the total damage amount of the surface protection film is reduced, and the clarity of the transmitted light image is improved. A film substrate "substantially free of particles" means that the particles do not affect the surface shape of the film. In addition, when the particle|grains do not affect the surface shape, the image sharpness may fall due to the light scattering at the interface of the resin component of a film base material and particle|grains. Therefore, the content of the particles in the film substrate is preferably 100 ppm or less, more preferably 50 ppm or less, still more preferably 30 ppm or less, and particularly preferably 10 ppm or less. Most preferably, the particle content of the film substrate is zero.

The surface of the film base material substantially free of particles is smooth and has low sliding properties, so that blocking may occur, and poor conveyance and winding in a roll-to-roll process may occur. In order to prevent blocking due to high smoothness, poor conveyance, and the like, a method of bonding another film with high slidability to a film base material, and a method of providing an easy-slip layer on the surface of the film base material are exemplified. The easy-slip layer provided on the surface of the film substrate may contain fine particles. When the easy-slip layer contains fine particles, when the particle size of the fine particles is small, the sliding property becomes insufficient. On the other hand, when the particle diameter of the fine particles contained in the easy-slip layer is too large, the total amount of damage to the surface protective film may increase due to scattering of visible light, and the transmitted light image clarity may decrease. The number average particle diameter of the fine particles is preferably 1 to 200 nm, more preferably 3 to 150 nm, and even more preferably 5 to 100 nm, from the viewpoint of both suppressing the scattering of visible light by the easy-slip layer and imparting slidability.

[Adhesive layer]

A highly transparent adhesive can be used for the adhesive layer 2 . The total light transmittance of the adhesive layer 2 is preferably 80% or more, more preferably 85% or more, and further preferably 90% or more. The haze of the pressure-sensitive adhesive layer 2 is preferably 1% or less, more preferably 0.7% or less, and further preferably 0.5% or less.

The composition of the adhesive constituting the adhesive layer 2 is not particularly limited, and an acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyamide, polyvinyl ether, vinyl acetate/chlorine can be appropriately selected and used. The composition of the base polymer is made of ethylene copolymer, modified polyolefin, epoxy-based, fluorine-based, rubber-based polymers such as natural rubber and synthetic rubber. In particular, from the viewpoint of being excellent in adhesiveness and optical transparency, it is preferable to use an acrylic adhesive based on an acrylic polymer and a urethane based on a urethane polymer. It is an adhesive and a silicone-based adhesive based on a silicone-based polymer.

<Acrylic adhesive>

As the acrylic base polymer of the acrylic adhesive, a polymer having a monomer unit of an alkyl (meth)acrylate as a main skeleton is suitably used. In addition, in this specification, "(meth)acrylic acid" means acrylic acid and/or methacrylic acid.

As the alkyl (meth)acrylate, an alkyl (meth)acrylate having an alkyl group of 1 to 20 carbon atoms is suitably used. For example, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, (meth)acrylate ) tert-butyl acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, (meth)acrylate base) 2-ethylhexyl acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate Esters, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isotridecyl (meth)acrylate, (meth)acrylic acid tetradecyl ester, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, ( Octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, aralkyl (meth)acrylate, and the like.

The content of the alkyl (meth)acrylate is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more with respect to the total amount of monomer components constituting the acrylic polymer. The acrylic polymer may be a copolymer of a plurality of alkyl (meth)acrylates. The arrangement of the constituent monomer units may be random or block.

The acrylic polymer preferably contains a monomer component having a crosslinkable functional group as a copolymerization component. As a monomer which has a crosslinkable functional group, a hydroxyl group-containing monomer and a carboxyl group-containing monomer are mentioned. Among them, it is preferable to contain a hydroxyl group-containing monomer as a copolymerization component. A hydroxyl group and a carboxyl group serve as a reaction point with a crosslinking agent described later. By introducing a crosslinked structure into the base polymer, the cohesive force of the pressure-sensitive adhesive is improved, moderate adhesive force to the adherend is exhibited, and re-peeling of the surface protective film from the adherend tends to be facilitated.

Examples of hydroxyl-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxy (meth)acrylate. Hexyl ester, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl acrylate, etc. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid.

In addition to the above-mentioned acrylic polymer, as a comonomer component, an acid anhydride group-containing monomer, a caprolactone adduct of acrylic acid, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, and the like can be used. In addition, as the modifying monomer, vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine can also be used , vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxamides, styrene, α-methylstyrene, N-vinylcaprolactam and other vinyl monomers; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; polyethylene glycol (meth)acrylate, poly Glycol acrylate monomers such as propylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate; tetrahydrofurfuryl (meth)acrylate , Acrylate monomers such as fluorine (meth)acrylate, silicone (meth)acrylate, 2-methoxyethyl acrylate, etc.

The ratio of the comonomer component in the acrylic polymer is not particularly limited. For example, in the case of using a hydroxyl group-containing monomer and a carboxyl group-containing monomer as the comonomer component for the purpose of introducing a crosslinking point, the hydroxyl group-containing monomer and the carboxyl group-containing monomer are used. The total content of the carboxyl group-containing monomer is preferably about 1 to 20%, and more preferably about 2 to 15% with respect to the total amount of the monomer components constituting the acrylic polymer.

The acrylic polymer is obtained by polymerizing the above-mentioned monomer components by various known methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization. The solution polymerization method is preferable from the viewpoints of the balance of properties such as adhesive force and holding force of the adhesive, cost, and the like. As the solvent for solution polymerization, ethyl acetate, toluene, or the like can be used. The solution concentration is usually about 20 to 80% by weight. As a polymerization initiator, various well-known polymerization initiators, such as an azo type and a peroxide type, can be used. In order to adjust the molecular weight, a chain transfer agent can be used. The reaction temperature is usually about 50 to 80°C, and the reaction time is usually about 1 to 8 hours.

The molecular weight of the acrylic polymer can be appropriately adjusted so that the pressure-sensitive adhesive layer 2 has a desired adhesive force. For example, the weight average molecular weight in terms of polystyrene is about 50,000 to 2,000,000, preferably 70,000 to 1,800,000. about, more preferably about 100,000 to 1,500,000, still more preferably about 200,000 to 1,000,000. In addition, when introducing a crosslinked structure into an acrylic base polymer, it is preferable that the molecular weight of the polymer before introduction of a crosslinked structure is the said range.

For the purpose of adjusting the adhesive force of the pressure-sensitive adhesive layer 2 or the like, a crosslinked structure may be introduced into the base polymer. For example, a crosslinking structure is introduced into the acrylic polymer by adding a crosslinking agent to the solution after polymerization and heating as necessary. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelate compounds Department of cross-linking agents, etc. Among them, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent are preferred from the viewpoints of high reactivity with the hydroxyl group and carboxyl group of the acrylic polymer and easy introduction of the crosslinked structure. These crosslinking agents react with functional groups such as hydroxyl groups and carboxyl groups introduced into the polymer to form a crosslinked structure.

As the isocyanate-based crosslinking agent, a polyisocyanate having two or more isocyanate groups in one molecule is used. Examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate. Alicyclic isocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate and other aromatic isocyanates; trimethylolpropane/toluene diisocyanate trimerization adducts (for example, "CORONATE L" manufactured by Tosoh Corporation), trimethylolpropane/hexamethylene diisocyanate trimer adducts (for example, "CORONATE HL" manufactured by Tosoh Corporation), Trimethylolpropane adduct of xylylene diisocyanate (for example, "TAKENATE D110N" manufactured by Mitsui Chemicals), isocyanurate of hexamethylene diisocyanate (for example, "CORONATE" manufactured by Tosoh Corporation) HX") and other isocyanate adducts, etc.

As the epoxy-based crosslinking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule is used. The epoxy group of the epoxy-based crosslinking agent may be a glycidyl group. Examples of epoxy-based crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N- Diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol Alcohol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitan polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, triglyceride Methylol propane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol Diglycidyl ether, bisphenol-S-diglycidyl ether, etc. As the epoxy-based crosslinking agent, commercially available products such as "DENACOL" manufactured by Nagase ChemteX Corporation and "TETRAD X" and "TETRAD C" manufactured by Mitsubishi Gas Chemical Co., Ltd. can be used.

A crosslinked structure is introduced by adding a crosslinking agent to the polymerized acrylic polymer. The amount of the crosslinking agent to be used may be appropriately adjusted according to the composition, molecular weight, target adhesion properties, and the like of the polymer. The amount of the crosslinking agent to be used is preferably 1.5 parts by weight or more, more preferably 100 parts by weight of the acrylic polymer, in order to make the pressure-sensitive adhesive have moderate cohesion and adjust the peeling force when peeling the protective film from the adherend to an appropriate range. 2 parts by weight or more, more preferably 2.5 parts by weight or more. The amount of the crosslinking agent to be used is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and even more preferably 10 parts by weight or less, based on 100 parts by weight of the acrylic polymer in order to have appropriate adhesiveness to the adherend.

<Urethane adhesive>

As the urethane-based base polymer of the urethane-based adhesive, a reaction product of a polyol and a polyisocyanate compound is used.

(Polyol)

Examples of polyols include polyols (diols) having two hydroxyl groups in one molecule, polyols (triols) having three hydroxyl groups in one molecule, and polyols (tetraols) having four hydroxyl groups in one molecule. ), a polyol (pentanol) having five hydroxyl groups in one molecule, a polyol (pentanol) having five hydroxyl groups in one molecule, a polyol (hexanol) having six hydroxyl groups in one molecule, and the like.

As the polyol component of the urethane-based base polymer, polymer polyols such as polyester polyol, polyether polyol, polycarbonate polyol, and caprolactone polyol are preferable. The number average molecular weight of the polyol is preferably about 400 to 30,000, more preferably about 1,000 to 25,000, and even more preferably about 3,000 to 20,000.

The polyester polyol is a polyester having a hydroxyl group at the terminal, and is obtained by reacting a polybasic acid and a polyhydric alcohol so that the alcohol equivalent is excessive with respect to the carboxylic acid equivalent. As the polybasic acid component and the polyol component constituting the polyester polyol, a combination of a dibasic acid and a diol is preferable.

Examples of dibasic acid components include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; hexahydrophthalic acid, tetrahydrophthalic acid, 1,3-cyclohexane Alicyclic dicarboxylic acids such as alkanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid Aliphatic dicarboxylic acids such as acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, and octadecanedicarboxylic acid; acid anhydrides, lower alcohol esters, and the like of these dicarboxylic acids.

Examples of glycol components include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 1 ,6-hexanediol, 1,8-octanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, 1,4-cyclohexane Alkane dimethanol, 1,4-cyclohexanediol, bisphenol A, bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, etc.

Polyether polyols are obtained by ring-opening addition polymerization of alkylene oxides on polyols. As an alkylene oxide, ethylene oxide, propylene oxide, butylene oxide, ethylene oxide, tetrahydrofuran, etc. are mentioned. As a polyhydric alcohol, the above-mentioned glycol, glycerol, trimethylolpropane, etc. are mentioned.

Examples of polycarbonate polyols include polycarbonate polyols obtained by polycondensation reaction of diol components and phosgene; diol components combined with dimethyl carbonate, diethyl carbonate, dipropyl carbonate, carbonic acid Polycarbonate obtained by transesterification condensation of carbonic acid diesters such as diisopropyl, dibutyl carbonate, ethylbutyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, and dibenzyl carbonate Ester polyols; copolycarbonate polyols obtained by combining two or more polyol components; polycarbonate polyols obtained by esterification of the above-mentioned various polycarbonate polyols and carboxyl-containing compounds; Polycarbonate polyols obtained by etherification of various polycarbonate polyols and hydroxyl-containing compounds; polycarbonate polyols obtained by transesterification of the above-mentioned various polycarbonate polyols with ester compounds; Polycarbonate polyols obtained by transesterification of the above-mentioned various polycarbonate polyols and hydroxyl-containing compounds; polyester-based polycarbonates obtained by polycondensation of the above-mentioned various polycarbonate polyols and dicarboxylic acid compounds Polyols; copolyether-based polycarbonate polyols obtained by copolymerizing the above-mentioned various polycarbonate polyols and alkylene oxides, and the like.

Examples of polycaprolactone polyols include caprolactone-based polyester diols obtained by ring-opening polymerization of cyclic ester monomers such as ε-caprolactone and σ-valerolactone.

A polyol containing a triol as a urethane-based base polymer is preferable from the viewpoints of improving the cohesive force of the adhesive, exhibiting moderate adhesive force to the adherend, and being excellent in releasability from the adherend Element. As the high molecular weight triol, a polyether polyol obtained by ring-opening addition polymerization of a triol such as glycerin and trimethylolpropane and an alkylene oxide is preferably used.

The content of the triol with respect to the entire polyol component constituting the urethane-based base polymer is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, and even more preferably 90% by weight or more.

When a high molecular weight triol is used as the polyol component of the urethane-based base polymer, it is preferable to use a combination of a triol having a number average molecular weight of 7,000 to 20,000, a triol having a number average molecular weight of 2,000 to 6,000, and a number average molecular weight. Triols with a molecular weight of 400-1900, more preferably a triol with a number-average molecular weight of 8,000-15,000, a triol with a number-average molecular weight of 2,000-5,000, and a triol with a number-average molecular weight of 500-1,800, more preferably in combination A triol having a number average molecular weight of 8000 to 12000, a triol having a number average molecular weight of 2000 to 4000, and a triol having a number average molecular weight of 500 to 1500 are used. By using three kinds of triols having different molecular weights in combination, it becomes easy to obtain a urethane-based pressure-sensitive adhesive that can achieve both adhesiveness to an adherend and releasability.

(polyisocyanate)

The polyisocyanate used for formation of the urethane-based base polymer may be any of aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates.

Examples of aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3- Butylene diisocyanate, dodecylidene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, etc.

Examples of alicyclic polyisocyanates include 1,3-cyclopentene diisocyanate, 1,3-cyclohexanediisocyanate, 1,4-cyclohexanediisocyanate, isophorone diisocyanate, hydrogenated Diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated tetramethyl xylylene diisocyanate, and the like.

Examples of aromatic polyisocyanates include phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylene Methane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene Diisocyanate, etc.

As the polyisocyanate, derivatives of the above-mentioned polyisocyanate compounds can also be used. Examples of derivatives of polyisocyanate compounds include dimers of polyisocyanates, trimers of polyisocyanates (isocyanurates), polymerized MDI, adducts with trimethylolpropane, and biuret modification. body, allophanate-modified body, urea-modified body, etc. The polyisocyanate may be a polyisocyanate obtained by adding protective groups such as oxime and lactam to the terminal isocyanate group. Since the protecting group is removed from the isocyanate group by heating, the isocyanate group reacts with the hydroxyl group of the polyol.

As the polyisocyanate, a urethane prepolymer having an isocyanate group at the terminal can be used. A urethane prepolymer having an isocyanate group at a terminal can be obtained by reacting a polyol and a polyisocyanate so that the polyisocyanate is excessive.

(other ingredients)

By mixing the above-mentioned polyol and polyisocyanate, a urethane-based base polymer can be obtained. The urethane-based adhesive may contain reactive components other than polyols and polyisocyanates.

For example, the urethane-based adhesive may contain a chain extender as a copolymerization component in addition to the polyol and the polyisocyanate. Examples of the chain extender include sorbitol, 1,2,3,6-hexanetetraol, 1,4-sorbitan, 1,2,4-butanetriol, 1,2,5- Polyols with 3 or more hydroxyl groups such as pentanetriol, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol; ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol , 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 1,6-hexanediol, propylene glycol and other glycols; dimethylolacetic acid, dimethylolbutane Acid, dimethylol propionic acid, dimethylol butyric acid, dimethylol valeric acid and other dihydroxyalkyl alkanoic acids, dihydroxysuccinic acid and other compounds with free carboxyl groups; ethylenediamine, propylenediamine, hexamethylenediamine Alicyclic diamines such as methylene diamine, 1,4-butanediamine, and aminoethylethanolamine; alicyclic diamines such as isophorone diamine and 4,4'-dicyclohexylmethanediamine; benzene Aromatic diamines such as dimethyldiamine and toluenediamine, and the like.

The urethane-based adhesive may contain a fatty acid ester. As the fatty acid ester, a fatty acid ester having a molecular weight of about 200 to 400 is preferably used. Specific examples of fatty acid esters include polyoxyethylene bisphenol A laurate, butyl stearate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, and monobehenate. Glycerides, Cetyl 2-Ethylhexanoate, Isopropyl Myristate, Isopropyl Palmitate, Cholesteryl Isostearate, Lauryl Methacrylate, Methyl Coconut Fatty Acid, Methyl Laurate, Methyl Oleate, Methyl Stearate, Myristyl Myristate, Octyldodecyl Myristate, Pentaerythritol Monooleate, Pentaerythritol Monostearate, Pentaerythritol Tetrapalmitate, Stearic Acid Stearate, isotridecyl stearate, triglyceride 2-ethylhexanoate, butyl laurate, octyl oleate, etc.

The mixing ratio of the fatty acid ester in the urethane-based adhesive is, for example, preferably 5 to 50% by weight, more preferably 8 to 40% by weight, and even more preferably 10 to 30% by weight relative to 100 parts by weight of the polyol.

The urethane-based adhesive may contain modified silicone oil such as polyether-modified silicone oil. As the modified silicone oil, a side-chain type polyether-modified silicone oil, a double-end type polyether-modified silicone oil, and the like can be mentioned. Among these, the polyether-modified silicone oil of both terminal type is preferable.

<Silicone-based adhesive>

As the silicone-based base polymer of the silicone-based binder, peroxide-crosslinking type silicone, addition reaction type silicone, and the like are exemplified. Among them, an addition reaction type silicone is preferable, and a phenyl group-containing organopolysiloxane is particularly preferable. Examples of the phenyl group-containing organopolysiloxane include polyalkylphenylsiloxanes such as polymethylphenylsiloxane and polyethylphenylsiloxane. The addition reaction-type silicone-based adhesive composition preferably contains a silicone rubber and a silicone resin.

(silicone rubber)

As the silicone rubber, a phenyl group-containing organopolysiloxane is preferable, and among these, a silicone rubber containing an organopolysiloxane having methylphenylsiloxane as a main structural unit is preferable. The organopolysiloxane in the silicone rubber may have functional groups such as vinyl groups as needed. The weight average molecular weight of the organopolysiloxane is preferably 150,000 to 1,500,000, more preferably 280,000 to 1,000,000, and further preferably 500,000 to 900,000.

(silicone resin)

As the silicone resin, for example, a silicone resin containing an organopolysiloxane containing an M unit selected from the group consisting of the structural unit "R ₃ -Si _1/2 ", a At least one of the Q unit composed of the structural unit "SiO ₂ ", the T unit composed of the structural unit "R-SiO _3/2 ", and the D unit composed of the structural unit "R ₂ -SiO" (total )polymer. In addition, R in the said structural unit is a hydrocarbon group or a hydroxyl group. As a hydrocarbon group, an alkyl group, a cycloalkyl group, an aryl group, etc. are mentioned. The ratio of the "M unit" in the silicone resin is preferably 0.3 to 1.5 times, more preferably 0.5 to 1.3 times the ratio of "at least one unit selected from the group consisting of Q unit, T unit and D unit".

The organopolysiloxane in the above-mentioned silicone resin may have a functional group such as a vinyl group if necessary. The weight average molecular weight of the organopolysiloxane in the silicone resin is preferably 1,000 to 20,000, and more preferably 1,500 to 10,000.

The compounding ratio of the silicone rubber and the silicone resin in the silicone-based adhesive is preferably 100 to 220 parts by weight, and more preferably 120 to 180 parts by weight, relative to 100 parts by weight of the silicone rubber.

(crosslinking agent)

In the silicone-based adhesive, the silicone rubber and the silicone resin may be in a mixed state, or the silicone rubber and the silicone resin may react to form a condensate or a partial condensate. The silicone rubbers, the silicone resins, or the silicone rubbers and the silicone resins may be combined with each other via a crosslinking agent. As the crosslinking agent, a silicone-based crosslinking agent, a peroxide-based crosslinking agent, and the like are preferable.

As the siloxane-based crosslinking agent, a polyorganohydrogensiloxane containing two or more hydrosilanes (SiH) in one molecule is preferable. The cross-linked structure is introduced by the hydrosilylation reaction of the vinyl group contained in the silicone rubber and the silicone resin and the hydrosilane. In the polyorganohydrogensiloxane, various organic groups other than the hydrogen atom may be bonded to the silicon atom to which the hydrogen atom is bonded. Examples of the organic group include alkyl groups such as methyl and ethyl; aryl groups such as phenyl; and halogenated alkyl groups. Among them, from the viewpoint of synthesis and handling, an alkyl group is preferable, and a methyl group is particularly preferable. The skeleton structure of the polyorganohydrogensiloxane may be any of linear, branched, and cyclic, but linear is preferred.

As the silicone-based adhesive composition, commercially available products such as "X-40-3306" manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

<Adhesive composition>

The adhesive composition contains a base polymer (or its constituent monomer components), and if necessary, a crosslinking agent and a solvent. The adhesive composition may contain a polymerization catalyst, a crosslinking catalyst, a silane coupling agent, an adhesiveness imparting agent, a plasticizer, a softener, an anti-deterioration agent, a filler, and a coloring agent within a range that does not impair the properties of the present invention. additives, UV absorbers, antioxidants, surfactants, antistatic agents, etc.

<Formation of pressure-sensitive adhesive layer>

By roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, A pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive composition on a base material by lip coating, die coating, and the like, and drying and removing the solvent if necessary. As a drying method, an appropriate method can be suitably used. The heating drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, further preferably 70°C to 170°C. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, still more preferably 10 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

When the adhesive composition contains a crosslinking agent, it is preferable to perform crosslinking by heating or aging simultaneously with drying of the solvent or after drying of the solvent. When the adhesive composition contains the constituent monomer components of the base polymer, it is preferable to polymerize by heating or aging. The heating temperature and the heating time are appropriately set according to the type of the monomer and the crosslinking agent to be used, but are usually in the range of 20°C to 160°C for about 1 minute to 7 days. The heating for drying and removing the solvent may also serve as heating for polymerization or cross-linking.

The thickness of the pressure-sensitive adhesive layer 2 is preferably 2 μm or more, and more preferably 3 μm or more, from the viewpoint of improving the adhesive force to the adherend and suppressing the reduction in image sharpness due to the incorporation of air bubbles or the like. The upper limit of the thickness of the adhesive layer is not particularly limited. From the viewpoint of maintaining transparency, the thickness of the adhesive layer 2 may be 150 μm or less, 100 μm or less, 75 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less. When re-peeling is required for the surface protective film, the thickness of the pressure-sensitive adhesive layer 2 is preferably 100 μm or less from the viewpoint of facilitating re-peeling from the adherend.

A surface protection film can be obtained by laminating the pressure-sensitive adhesive layer 2 on the film base material 1 . The pressure-sensitive adhesive layer 2 may be directly formed on the film base material 1 , or a pressure-sensitive adhesive layer formed in a sheet shape on another base material may be transferred onto the film base material 1 . By attaching the separator 5 to the pressure-sensitive adhesive layer 2, a separator-attached surface protection film is obtained. The base material used for formation of the pressure-sensitive adhesive layer can be used as the separator 5 as it is.

As the separator 5, plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films are preferably used. The thickness of the separator is usually 3 to 200 μm, preferably about 10 to 100 μm, and more preferably about 15 to 50 μm. The contact surface of the separator 5 with the pressure-sensitive adhesive layer 2 is preferably subjected to a mold release treatment by a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based mold release agent, or silica powder or the like. .

[Application of surface protective film]

By bonding the surface protection film of the present invention to various adherends, damage to the surface of the adherend and breakage due to impact can be prevented.

The surface protective film of the present invention has good adhesiveness to glass, acrylic plates, etc., high transparency, and high image clarity of transmitted light, so that it can be used as a surface protective film for various optical members. Examples of optical members include optical films such as polarizers, retardation films, optical compensation films, viewing angle widening films, viewing angle control films, light enhancement films, antireflection films, reflective sheets, transparent conductive films, prism sheets, and light guide plates; liquid crystals; Image display panels such as panels and organic EL panels; image display devices incorporating image display panels; lenses, etc. An image display panel and an image display device can be formed by assembling in a state where a surface protection film is bonded to an optical film as an optical member.

Since the surface protection film of the present invention has high image definition of transmitted light, it is unlikely to be an obstacle to optical inspection. Therefore, optical inspection such as brightness inspection can be accurately performed in the state where the surface protection film is bonded, and this contributes to the improvement of the efficiency and accuracy of the optical inspection. In addition, the surface protective film of the present invention has little light scattering and hardly causes glare of transmitted light, so it is also suitable for use as a surface protective film for displays such as liquid crystal display devices and organic EL display devices.

Example

Hereinafter, the present invention will be described more specifically with reference to the production examples of the surface protective film, but the present invention is not limited to these examples.

[Example 1]

<Polymerization of Acrylic Polymer A>

In a reaction vessel equipped with a thermometer, a stirrer, a condenser, and a nitrogen gas introduction pipe, 96.2 parts by weight of 2-ethylhexyl acrylate (2EHA), 3.8 parts by weight of hydroxyethyl acrylate (HEA), and 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added with 150 parts by weight of ethyl acetate, and nitrogen gas was introduced while stirring slowly at 23° C. for nitrogen replacement. Then, the liquid temperature was maintained at around 65°C, and a polymerization reaction was performed for 6 hours to prepare a solution of the acrylic polymer A (concentration: 40% by weight). The weight average molecular weight of the acrylic polymer A was 540,000.

<Preparation of adhesive composition>

Ethyl acetate was added to the solution of the acrylic polymer A to dilute to a concentration of 20% by weight. To 500 parts by weight of this solution (100 parts by weight of solid content), 1.5 parts by weight of a solution obtained by diluting a polyether compound (“Aqualon HS-10” manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) to 10% with ethyl acetate (0.15 parts by weight of solid content) was added. parts by weight), 5 parts by weight of isocyanurate of hexamethylene diisocyanate (“CORONATE HX” manufactured by Tosoh Corporation) as a crosslinking agent, and dibutyltin dilaurate (1 part by weight) as a crosslinking catalyst % by weight of ethyl acetate solution) 3 parts by weight (solid content 0.03 parts by weight) was stirred to prepare an acrylic pressure-sensitive adhesive solution.

<Production of surface protective film>

The above-mentioned acrylic adhesive solution was coated on the non-formed surface of the easy-slip layer of a non-particulate polyester film (“Lumirror U41” manufactured by Toray Co., Ltd., thickness 38 μm) equipped with a nano-particle-containing easy-slip layer on one side, at 130 Heating was performed for 2 minutes at °C to form an adhesive layer with a thickness of 10 μm. The release-treated surface of the separator (polyester film having a thickness of 25 μm with silicone release treatment on one side) was bonded to the surface of the pressure-sensitive adhesive layer to obtain a surface protection film with a separator.

[Example 2]

<Polymerization of Acrylic Polymer B>

In a reaction vessel equipped with a thermometer, a stirrer, a condenser, and a nitrogen introduction pipe, 95 parts by weight of butyl acrylate, 5 parts by weight of acrylic acid, and 0.2 parts by weight of AIBN as a polymerization initiator and ethyl acetate as monomer components 186 parts by weight were added together, and nitrogen was introduced to perform nitrogen substitution while stirring slowly at 23°C. Then, the liquid temperature was kept at 63° C. and a polymerization reaction was performed for 10 hours to prepare a solution of the acrylic polymer B (concentration: 35% by weight). The weight average molecular weight of the acrylic polymer B was 500,000.

<Preparation of adhesive composition and preparation of surface protective film>

Ethyl acetate was added to the solution of the acrylic polymer B to dilute to a concentration of 20% by weight. To 500 parts by weight of this solution (100 parts by weight of solid content), 7 parts by weight of a tetrafunctional epoxy compound (“TETRAD C” manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a crosslinking agent was added and stirred to prepare an acrylic adhesive agent solution. Using the obtained acrylic pressure-sensitive adhesive solution, it carried out similarly to Example 1, and produced the surface protection film with a separator.

[Example 3]

As a polyol, 85 parts by weight of a polyether polyol having three hydroxyl groups and a number-average molecular weight of 10,000 (“PREMINOL S3011” manufactured by Asahi Glass) and a polyether polyol having three hydroxyl groups and a number-average molecular weight of 3,000 (“Sanyo Chemical Co., Ltd.” 13 parts by weight of SANNIX GP3000"), 2 parts by weight of polyether polyol having 3 hydroxyl groups and a number-average molecular weight of 1,000 ("SANNIX GP1000" manufactured by Sanyo Chemicals), isocyanurate of hexamethylene diisocyanate as polyisocyanate 13.3 parts by weight of an acid ester (“CORONATE HX”, manufactured by Tosoh Corporation), 0.12 parts by weight of iron acetylacetonate (Natsume 2nd Iron, manufactured by Nippon Chemical Industries, Ltd.) as a catalyst, and a hindered phenol-based antioxidant (“Irganox 1010 manufactured by BASF”) ") 0.5 parts by weight, cetyl 2-ethylhexanoate as fatty acid ester ("SALACOS 816T" manufactured by The Nisshin OilliO Group, Ltd.) 5 parts by weight, 1-ethyl-3-methylimidazolium bismuth (Fluoromethanesulfonyl)imide (“AS110” manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) 0.5 parts by weight, double-ended polyether-modified silicone oil (KF-6004, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.025 parts by weight, and as 210 parts by weight of ethyl acetate as the dilution solvent was mixed to prepare a urethane-based adhesive solution.

Using the obtained urethane-based adhesive solution, it carried out similarly to Example 1, and produced the surface protection film with a separator.

[Example 4]

100 parts by weight of an addition reaction type silicone-based binder (“X-40-3306” manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.2 parts by weight of a platinum catalyst (“CAT-PL-50T” manufactured by Shin-Etsu Chemical Co., Ltd.) , and 100 parts by weight of toluene as a solvent to prepare a silicone-based adhesive solution.

Using the obtained silicone-based adhesive solution, it carried out similarly to Example 1, and produced the surface protection film with a separator.

[Examples 5 to 7, Comparative Examples 1 to 3]

The addition amount of the epoxy-based crosslinking agent (TETRAD C) and the thickness of the pressure-sensitive adhesive sheet in Example 2 were changed as shown in Table 1. Except for this, it carried out similarly to Example 2, and produced the surface protection film with a separator.

[Examples 8 to 10, Comparative Examples 4 and 5]

In Example 1, the film substrate shown in Table 1 was used instead of the particle-free polyester film (Lumirror U41). Except for this, it carried out similarly to Example 1, and produced the surface protection film with a separator.

[Comparative Example 6]

In Example 2, the addition amount of the epoxy-based crosslinking agent (TETRAD C), the thickness of the pressure-sensitive adhesive sheet, and the type of the film substrate were changed as shown in Table 1. Except for this, it carried out similarly to Example 2, and produced the surface protection film with a separator.

[Measurement method and evaluation method]

<Adhesion>

The surface protection film was cut out to a size of 25 mm in width and 100 mm in length, and after peeling off the separator, it was roll-bonded to an acrylic plate ("ACRYLITE" manufactured by Mitsubishi Chemical Corporation, thickness 0.25 MPa, feed speed 0.3 m/min) : 2mm, width: 70mm, length: 100mm). The sample was left standing for 30 minutes in an environment with a temperature of 23° C. and a relative humidity of 50%, and then a peel test was performed in the same environment at a peel angle of 180° and a tensile speed of 30 m/min, and the 180° peel force was measured.

<Haze>

The separator was peeled off from the surface protective film, and light was irradiated from the film base side of the surface protective film with a haze meter (“NDH-5000” manufactured by Nippon Denshoku Industries Co., Ltd.), and the haze was measured according to JIS K 7136.

<Total damage amount>

The surface protection film was cut out to a size of 100 mm × 100 mm, and the separator was peeled off, and then pressure-bonded to a micro glass slide (“Micro Slide Glass” manufactured by Matsunami Glass Industry Co., Ltd., thickness: 1.35 mm, 100 mm × 100 mm) . While moving the sample in one direction at a linear velocity of 5 m/min, a surface light source (light source: "LT-200SW" manufactured by CCS, lighting amplifier: "PSB3-30024" manufactured by CCS, lighting cable: FCB-10-1 , 24SQ-ME7”) irradiated light from the glass plate side, and the transmitted light was photographed with a 4096-pixel line scan camera (“XG-HL04M” manufactured by KEYENCE CORPORATION) to obtain 8bit (256 levels) gray with an area of 102.4mm×12.5mm The captured image of the degree level. The scanning rate of the line scan camera is adjusted so that 1 pixel in the feeding direction corresponds to 25 μm. The distance between the light source and the sample (the distance in the normal direction of the surface protection film) during the imaging is set to 200 mm The distance between the sample and the line scan camera is set to 210 mm, and the horizontal position of the line scan camera is set at a position where the received light amount becomes half of the maximum light amount (approximately 120 levels). In this measurement, 1 pixel of the line scan camera corresponds to A 25 μm x 25 μm area of the sample.

An area of 200 × 200 pixels (corresponding to the area of 5 mm × 5 mm of the sample) was cut out from the obtained captured image, and a damage inspection tool made by KEYENCE CORPORATION was used in the section size: 4, damage level threshold: 3 The damage detection was performed under the conditions, and the total damage amount in the analysis area was obtained.

<Adhesion and image clarity>

The surface protection film was cut out to a size of 45 mm in width and 50 mm in length, and after peeling off the separator, it was pressed with a hand roller to a water edge glass slide (Suzumo スライドガLAS, "S200200" manufactured by Matsunami Glass Industry Co., Ltd., thickness : 1.3mm, width: 45mm, length: 50mm). The sample was visually observed, and the presence or absence of air bubbles between the surface protection film and the glass plate was evaluated according to the following criteria.

A: Almost no bubbles are seen

B: Bubbles can be seen locally

C: Air bubbles can be seen on the entire surface

The image sharpness of the above-mentioned sample was measured by the transmission method according to JISK7374 using an image sharpness measuring instrument (“ICM-1” manufactured by Suga Test Instruments Co., Ltd.). The optical comb uses 0.125mm.

<Visual Recognition>

The separator was peeled off from the surface protection film, attached to the screen of a smartphone equipped with an organic EL display (“Galaxy S8+” manufactured by Samsung Electronics), and the screen was viewed from a distance of 150 mm while a green image was displayed. The presence or absence of glare was evaluated by the following criteria.

A: No glare at all

B: Glare is hardly felt

C: Glare is felt

D: Glare is very clearly felt

Table 1 shows the structure of the surface protective film of each production example (type of film base material, composition and thickness of the adhesive) and evaluation results of the surface protective film. Details of the film substrate are as follows.

U41: A particle-free biaxially stretched polyester film provided with an easy-slip layer on one side (“Lumirror U41” manufactured by Toray Co., Ltd., thickness 38 μm)

TA044: Particle-free biaxially stretched high birefringence polyester film with an easy-slip layer on one side (“COSMOSHINE TA044” manufactured by Toyobo, thickness 80 μm)

T101: Particle-containing low-haze biaxially stretched polyester film (“Diafoil T101-38” manufactured by Mitsubishi Chemical Corporation, thickness 38 μm)

T100: Particle-containing biaxially stretched polyester film (“Diafoil T100-75S” manufactured by Mitsubishi Chemical Corporation, thickness 75 μm)

T100C: Biaxially stretched polyester film containing particles ("Diafoil T100C#38" manufactured by Mitsubishi Chemical Corporation, thickness 38 μm)

Acrylic: Biaxially stretched film (thickness: 40 μm) made of imidized MS resin produced in the same manner as the “transparent protective film 1A” described in the Example of JP-A No. 2017-26939

COP: Cyclic olefin film (“ZEONOR FILM ZF-16” manufactured by Zeon Corporation, thickness 40 μm)

[Table 1]

The surface protection films of Examples 1 to 9 had good adhesion to the acrylic plate, and also had good visibility of transmitted light. From the comparison between Example 5 and Example 6, it was observed that the larger the thickness of the adhesive layer, the larger the adhesive force to the acrylic sheet tends to be. In addition, according to the comparison between Example 2 and Example 5, and the comparison between Example 6 and Example 7, it was observed that as the amount of the cross-linking agent added to the adhesive composition increased, the adhesion to the acrylic sheet was improved. Tendency to decrease force.

In Comparative Example 1 with a small thickness of the pressure-sensitive adhesive layer, the adhesiveness to the adherend was low, and many air bubbles were observed between the adhesive layer and the adherend. In addition, in Comparative Example 1, significant glare was observed in the transmitted light, and the visibility was poor. In Comparative Example 2, compared with Comparative Example 1, the amount of the crosslinking agent was decreased, and the adhesive force was improved, but the image sharpness was low, and transmitted light glare was observed. From this result, even when the adhesiveness is high, when the thickness of the adhesive layer is small, minute air bubbles are easily mixed into the adhesive interface, and the visibility is lowered. In Comparative Example 3, the thickness of the pressure-sensitive adhesive layer was increased compared with Comparative Example 1, but since the amount of the crosslinking agent was large, the pressure-sensitive adhesive was hard and the adhesiveness with the adherend was insufficient.

In Comparative Examples 4 and 5 in which the same adhesive as in Example 1 was used and the types of film substrates were changed, the adhesiveness and adhesion between the surface protection film and the adherend were good, but the image sharpness was low. to transmitted light glare. In Comparative Example 6, although the addition amount of the crosslinking agent in the adhesive composition was reduced, the adhesive force was greatly increased, but the improvement in visibility was not observed. The decrease in visibility in Comparative Examples 4 to 6 is considered to be caused by particles contained in the film base material.

In Examples 1 to 10 and Comparative Examples 1 to 6, a high correlation was observed between the total damage amount of the surface protection film and the clarity of the transmitted image. In addition, it is observed that the higher the clarity of the transmitted image, the less likely the glare of the transmitted light occurs, and the visibility tends to be improved.

From the above results, it was found that by adjusting the type of the film substrate, the composition of the adhesive, the thickness of the adhesive layer, etc., the total amount of the laminate (surface protective film) of the film substrate and the adhesive can be reduced. Surface protection film with high damage amount, high transmitted light image clarity, and excellent visibility of transmitted light from adherends.

Description of reference numerals

1 Film substrate

2 adhesive layers

5 Isolators

10, 13 Surface protection film

Claims (5)

1. A surface-protecting film comprising a film base and an adhesive layer fixedly laminated on a first main surface of the film base,

the surface protection film has a haze of 2% or less,

the surface protective film has an adhesion to an acrylic plate at a stretching speed of 30 m/min and a peel angle of 180 DEG of 0.03N/25mm or more,

the total damage amount of the surface protection film calculated from an image of 200 × 200 pixels obtained from an inspection area of 5mm × 5mm is 3000 or less.

2. The surface protection film according to claim 1, wherein the thickness of the adhesive layer is 2 μm or more.

3. The surface protective film of claim 1 or 2, wherein the film substrate is substantially free of particles.

4. The surface protection film according to any one of claims 1 to 3, wherein the adhesive layer contains 1 or more selected from the group consisting of an acrylic adhesive, a urethane adhesive, and a silicone adhesive.

5. An optical member having a protective film, wherein the surface protective film according to any one of claims 1 to 4 is bonded to a surface of the optical member.

Images